Normal hair is sometimes naturally so fine and limp and so lacking in body that it does not hold a hair set well. Frequently, the hair becomes even less bodied and is sometimes weakened as a result of being subjected to multiple chemically active cosmetic treatments, such as permanent waves and tints. Additionally, hair may be further weakened and weathered by other contributing factors, such as bleaching by exposure to sun and chlorinated swimming pool water.
Normal hair is also usually hydrophobic. However, many of the previously mentioned chemical treatments remove the natural hydrophobic components from the hair. Consequently, the relative porosity of the hair increases as its hydrophobicity decreases. As the porosity of the hair increases, it tends to pick up water and swell more readily. When the hair is weakened and porous, it is more vulnerable to stretching and breaking while it is water-swollen.
Routine grooming inevitably requires that wet hair be mechanically stretched and manipulated during shampooing, combing and setting on curlers. Additionally, currently popular hairstyles are achieved by "blow-drying" the freshly washed hair. In the "blow-dry" procedure, the hair is not set on curlers; rather the wet hair is brushed continuously until it is dry while a stream of heated air from a hand-held electric hair dryer is directed over the portion of the hair being brushed. Thus water-swollen hair that is in a weakened physical condition may snap and break or be mechanically damaged during blow drying.
This invention relates to a method of treating hair to strengthen it and improve its physical properties by treating the hair with compositions containing a water-dispersible non-toxic polyvalent metal salt of a mineral acid. The hair is strengthened by restoring its hydrophobicity and decreasing its porosity. The physical properties of the hair are improved by long-lasting conditioning benefits that resist removal by water or subsequent shampoo washings. The polyvalent metal salts have a cation selected from the group consisting of aluminum (III), cerium (III) and (IV), iron (III) and zirconium (IV) and an anion of a strong mineral acid.
Polyvalent metal salts are generally appreciated in the art primarily for their astringent effects on skin for antiperspirant activity. Hewitt et al. in U.S. Pat. No. 3,842,847, taught the use of astringent water-soluble salts of aluminum, hafnium, zirconium and zinc and the like in a shampoo and hair treatment to diminish scalp perspiration. By diminishing the perspiration on the scalp, less sebum transferred to the hair, so the hair stayed cleaner longer. Hewitt et al. reported antistatic, as well as anti-soiling, effects with aqueous rinses of aluminum chlorohydrate present in concentrations of at least 0.004 weight percent, preferably from 2 to 6 weight percent. The researchers believed the aluminum salt reacted with the hair keratin making it less anionic in nature and thus less "fly-away." However, for the purposes intended by Hewitt et al., the pH of the treatment and shampoo compositions were limited to the operable astringency range of the metal salts from 3 to 6.5. Also the hair had to be water rinsed after treatment until the pH of the rinse water was at least over 6.
The effectiveness of the method of this invention, as explained below, is not dependent on the astringent action, if any, of the polyvalent metal salt of aluminum or zirconium selected for use in hair-treating compositions used herein. For example, zinc salt, one of the astringent materials taught by Hewitt et al. is ineffective to achieve the results of this invention. Further the hair treating compositions of this invention, including those containing aluminum and zirconium salts similar to those taught by Hewitt et al., need not be rinsed from the hair. Indeed, the compositions are preferably allowed to remain in contact with the hair as explained below, and are effective for the purpose intended at salt concentrations well below known levels recognized for astringent antiperspirant effects.
Cassidy in U.S. Pat. No. 3,208,910, taught the use of a water-soluble zirconium carboxylate salt in a hair styling fluid for imparting body, moisture resistance and sheen to human hair. Zirconium acetate present in a concentration of 0.1 to 2 percent at a pH from about 3 to 6 was used for setting the hair. However, the hair tended to behave as if it were full of snarls and was extremely difficult to comb if the concentration exceeded 2 percent. Consequently, body and moisture-resistant effects could only be increased by including auxiliary dispersing agents, waxes and polymers or by washing the hair with a soap shampoo and forming an insoluble zirconium soap on the hair. The compositions of this invention are not so restricted, and the zirconium salts practiced as taught herein are those which were rejected by Cassidy as being less effective than carboxylate salts.
Commercially available products usually rely on resins or polymeric materials to produce bodying effects on the hair. However, these products usually provide no hydrophobic improvement against the known adverse effects of humidity in maintaining a hair style. In some cases, these materials make the hair hard to comb or may, themselves, absorb moisture. Attempts have been made to make hair hydrophobic by means of products that are applied to the hair in the form of oily hair dressings and creams where the product is left on the hair to act as a physical barrier against moisture. However such products provide a temporary effect that is removed when the user washes her or his hair. Frequently these products weigh the hair down with a dull coating, thereby sacrificing the bodying benefits desired by persons having fine, limp, porous hair. Thus, consumers face a dilemma in choosing which physical characteristics they wish to improve and which desirable characteristics they are willing to sacrifice to get the desired improvement.
A desirable hair treatment product, therefore, would strengthen the hair, especially porous hair, and provide a cosmetically pleasing, lasting improvement in the physical properties of hair.